Evaluation of copper nanoparticles for low temperature bonded interconnections

In this study, we evaluate the application of copper nanoparticles as a low temperature bonded interconnection. The copper nanoparticles have an organic passivation layer which stabilizes them, preventing spontaneous particle fusion and growth at ambient temperatures, as well as avoiding oxidation before its usage. Thermogravimetric analysis and differential scanning calorimetry show that the solvents and passivation layer can be removed completely from the copper nanoparticles paste by a sintering profile of up to 200°C. Cross sectional analysis show that the copper nanoparticles have fused to create a low porosity layer that gave good shear strength of the bonded joint. Moreover, Cu nanoparticles bonded samples demonstrate excellent thermal stability after 1000 h of aging at 150°C under normal ambient, as the shear strength of the joints increased instead without any observable oxidation of the Cu nanoparticles layer. Lastly, the addition of copper nanowires to the nanoparticles paste further improves the mechanical strength of the bonded interconnections due to the retardation of the crack propagation.